A large-scale integrated circuit (LSI) package is mounted on a motherboard, for example. Terminal bumps are arranged in a matrix on the motherboard for mounting the LSI package on the motherboard. An LSI chip is mounted on a package substrate in the LSI package. The LSI chip is surrounded by a stiffener on the front surface of the package substrate. The stiffener serves to increase the rigidity of the package substrate. A heat spreader is attached to the surface of the LSI chip. The stiffener is placed in a space between the package substrate and the heat spreader.
The terminal bumps include the outermost bump row. The outermost bump row is inscribed in a prism standing upright on the front surface of the package substrate. The contour of the stiffener coincides with that of the heat spreader. The outer periphery of the stiffener is inscribed in the prism. A bonding material is interposed between the stiffener and the package substrate and between the stiffener and the heat spreader. The stiffener is bonded to the package substrate and the heat spreader through the bonding material.